The present invention relates generally to catheters for performing medical procedures including percutaneous transluminal coronary angioplasty. More particularly, the present invention relates to catheters with improved shaft designs.
The use of intravascular catheters has become an effective method for treating many types of vascular disease. In general, an intravascular catheter is inserted into the vascular system of the patient and navigated through the vasculature to a desired target site. Using this method, virtually any target site in the patient""s vascular system may be accessed, including the coronary, cerebral, and peripheral vasculature. Examples of therapeutic purposes for intravascular catheters include percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA).
Intravascular catheters are commonly used in conjunction with a guidewire. A guidewire may be advanced through the patient""s vasculature until it has reached a target location. Once in place, a catheter may be threaded onto the guidewire and urged distally until the distal end of the catheter reaches a target location.
Intravascular catheters adapted for use with a guidewire typically are classified as over-the-wire (OTW) or single operator exchange (SOE). An OTW catheter includes a guidewire lumen extending from the distal tip of the catheter to the proximal end of the catheter. When intravascular catheters are used, it is common for physicians to remove one catheter and exchange it for another. While exchanging catheters, the guidewire must be held in place so as to keep its distal end near the target area. A portion of the guidewire is typically grasped by the physician in order to withdraw the first catheter while maintaining the distal end of the guidewire in the desired position. To properly anchor the guidewire, a portion of the guidewire must be exposed at all times so it is available for the physician to grasp. In the case of an OTW catheter, this requires that the length of the guidewire extending beyond the patient""s body be longer than the catheter. Consequently, in many cases intravascular catheters are longer than 200 cm or require guidewire extensions to facilitate exchange. Correspondingly, there may be more than 200 cm of wire extending from the patient. Managing this length of wire during a catheter exchange procedure is awkward, and typically requires more than one person. Additionally, contamination must be avoided by assuring that the guidewire is not dropped from the sterile field.
SOE catheters were developed in response to difficulties encountered when exchanging OTW catheters. Accordingly, SOE catheters have a relatively short guidewire lumen relative to the length of the catheter. Therefore, the length of guidewire extending beyond the body of the patient need only be slightly longer than the guidewire lumen of the catheter. The physician may anchor or hold the guidewire as the first catheter is removed from the body with the exchange occurring over the shorter guidewire lumen. The guidewire lumen of an SOE catheter typically includes a distal guidewire port disposed at the distal tip of the catheter and a proximal guidewire port disposed proximally of the distal end of the catheter.
When in use, intravascular catheters enter a patient""s vasculature at a convenient location and then are urged to a target region. Once the distal portion of the catheter has entered the patient""s vascular system the physician may urge the distal tip forward by applying longitudinal forces to the proximal portion of the catheter. For the catheter to effectively communicate these longitudinal forces it is desirable that the catheter have a high level of pushability and kink resistance particularly near the proximal end.
Frequently the path taken by a catheter through the vascular system is tortuous, requiring the catheter to change direction frequently. In some cases, it may even be necessary for the catheter to double back on itself. In order for the catheter to conform to a patient""s tortuous vascular system, it is desirable that intravascular catheters be very flexible, particularly near the distal end.
Further, while advancing the catheter through the tortuous path of the patients vasculature, physicians often apply torsional forces to the proximal portion of the catheter to aid in steering the catheter. Torsional forces applied on the proximal end must translate to the distal end to aid in steering. It is therefore desirable that the proximal portion of an intravascular catheter have a relatively high level of torquability to facilitate steering.
The need for this combination of performance features is often addressed by manufacturing a catheter that has two or more discrete tubular members having different performance characteristics. For example, a relatively flexible distal section may be connected to a relatively rigid proximal section. When a catheter is formed from two or more discrete tubular members, it is often necessary to form a bond between the distal end of one tubular member and the proximal end of another tubular member.
An approach used to enhance pushability and torquability of intravascular catheters is to construct the proximal end from hypodermic tubing, or a xe2x80x9chypotubexe2x80x9d. While a hypotube can add significant pushability and torquability to an intravascular catheter due to its intrinsic strength and rigidity, it can kink.
A need, therefore, exists for the manufacturing of SOE intravascular catheters to include shaft designs that maintain pushability, flexibility, and torquability while limiting the untoward properties of using a hypotube.
The present invention relates generally to catheters for performing medical procedures including percutaneous transluminal coronary angioplasty. More particularly, the present invention relates to catheters with improved shaft designs. Preferably, the catheter shaft comprises an elongate support member with proximal and distal ends, at least one gap within the elongate support member. In a preferred embodiment of the current invention, a sheath is disposed about the elongate support member.
In a preferred embodiment of the current invention, the gap defines a first edge and a second edge. Preferably, a first projection extends from the first edge and a second projection extends from the second edge. In an exemplary embodiment, the first projection and the second projection overlap. According to a preferred embodiment, the first edge and the second edge may further comprise additional projections.
In an exemplary embodiment of the current invention, a gap within the elongate support member is used to improve its properties. Preferably, the gap improves flexibility while retaining the desired level of pushability and torquability. The gap within the elongate support member may be formed by a number of methods. The methods of forming a gap may include, but are not limited to, cutting (for example laser cutting), sawing, and electrochemical masking.
In a particular embodiment of the current invention, a gap defines a first edge and a second edge. Preferably, the gap comprises a variable taper wherein the gap changes from the proximal to distal end. By introducing a taper, the level of flexibility may vary between proximal and distal ends. For example, the taper may result in a gap that is greater near the distal end. This could result in greater flexibility near the distal end of the catheter.
In an alternative embodiment of the current invention, the first projection and the second projection are interlocking. In an exemplary embodiment, the first projection is substantially rounded. By interlocking the projections, the elongate support member may retain pushability and torquability while increasing flexibility. Further, altering the shape of the projections can enhance desired flexibility changes throughout the elongate support member. For example, a rounded projection can vary in size along the longitudinal axis of the elongate support member. A specific example may include larger projections near the proximal end and smaller projections near the distal end. In this example, the smaller projections near the distal end may increase flexibility near the distal end of the elongate support member.
Additionally, the amount of gap formed between a plurality of projections can vary. For example, the gap between interlocking surfaces may be uniformly altered in differing embodiments. In this example, an elongate support member could be constructed that has increased gap length between interlocking projections at a proximal or distal end that may result in altered flexibility.
Further, the gaps formed between interlocking surfaces may vary along the longitudinal axis of the elongate support member. For example, the gap length may be greater near the distal end of the elongate support member. This may result in increased catheter shaft flexibility near the distal end.
Additionally, in alternative embodiments of the current invention, the elongate support member may comprise more than one piece. This multi-piece configuration may add beneficial properties to the catheter shaft including, but not limited to, increased flexibility, increased kink resistance, pushability, and torquability. One skilled in the art would be familiar with the advantages of manufacturing a multi-piece configuration that would be appropriate for multiple embodiments of the current invention. Further, the methods for producing a multi-piece elongate support member would be familiar to one skilled in the art.
In an alternative embodiment of the current invention, the first projection and the second projection are non-interlocking. The projections could manifest in a multiplicity of shapes according to differing embodiments of the current invention.
In an preferred embodiment of the current invention, the gap length for non-interlocking projections can be varied. For example, a projection may have a relatively longer gap in the longitudinal direction (along the longitudinal axis) of the catheter shaft and a relatively shorter gap in the direction perpendicular to the longitudinal axis of the elongate support member. In this example, the catheter shaft may have increased circumferential flexibility while allowing little axial movement. Multiple embodiments of the current invention can be derived that incorporate varied gaps along projections.
Additionally, the amount of gap formed between a plurality of projections can vary. For example, the gap between non-interlocking projections may be uniformly altered in differing embodiments. In this example, an elongate support member could be constructed that has increased gap length between non-interlocking projection near a proximal end or a distal end that may result in altered flexibility.
In an alternative embodiment of the current invention, the first projection and the second projection may comprise differing shapes. In multiple embodiments of the current invention, the projections could also have varying size and gap length as illustrated above. Further, multiple embodiments can be derived that incorporate varied gaps between projections as illustrated above. Similar alterations can be derived for modified projections of differing shapes.
In an alternative embodiment of the current invention, the first edge and the second edge defines a tapered and a non-tapered region. The taper forms a gap that changes from the proximal to the distal end. By introducing both a taper and a non-tapered region, the level of flexibility can vary between proximal and distal ends. For example, a non-tapered region may result in a less flexible region near the proximal end of the catheter and the taper may result in a gap that is greater near the distal end. This could result in greater flexibility near the distal end of the catheter.